Andy_Langton - 3:16 pm on Sep 22, 2012 (gmt 0)
If the link categorically goes to your domain name (and not a slight variation), then the symptoms point at hacking or malware.
If it's malware, then that would normally be installed on your own PC, usually at the browser level. This is easy to verify by testing with an alternate machine you can be certain isn't compromised. It doesn't sound like it will be the case here as a third party informed you of it.
Incidentally, here's a decent discussion on hacked site redirecting: [webmasterworld.com...]